This invention relates to a painting apparatus and process for painting inner panel regions of a motorcar vehicle body. The regions to be painted include (a) an inner panel portion in the front region of the vehicle body that includes an inner surface of a front lid such as a hood or the like, (b) an inner panel portion of the rear region of the vehicle body that includes an inner surface of a rear lid such as a trunk lid, a tail gate or the like, and (c) an inner panel portion of a door region on each side of the vehicle body that includes an inner surface of a door and a door trim portion.
One type of painting process for an inner panel region of a 2-door type motorcar vehicle body has been disclosed in Japanese Unexamined Patent Application publication Sho 56-144763. In this disclosure, a motorcar vehicle body is conveyed into a painting area or stage with its doors left open. A pair of front and rear painting robots, which are movable forwards and rearwards, are disposed on the left and right side portions of the painting stage. An inner panel portion of the front region of a vehicle body is painted by the front painting robots, and at the same time, the inner panel portions of the door regions on both the left and right sides of the vehicle body are painted by the rear painting robots. Thereafter, an inner panel portion of the rear region of the vehicle body is painted by the rear painting robots.
A similar painting process for a 4-door type motorcar vehicle body can be carried out by utilizing the foregoing conventional technique. That is, the 4-door type motorcar vehicle body is conveyed into a painting area or stage with its front doors and rear doors remaining open. The first step in painting a vehicle body involves painting an inner panel portion of the front region of the vehicle body by the front painting robots located on the left and right side portions of the painting stage. At the same time, inner panel portions of the rear door regions on both sides of the vehicle body are painted by the rear painting robots located on the body's left and right sides. Thereafter, the second step in painting involves painting the inner panel portions of the front door regions on both left and right sides of the vehicle body. These regions are painted by the front painting robots, and at the same time, an inner panel portion of a rear region of the vehicle body is painted by the pair of rear painting robots.
However, with the foregoing known process and the foregoing possible process, when the vehicle body is conveyed into the painting stage or when the pair of front painting robots is moved in order to carry out the second painting step after completion of the first painting step, the pair of front painting robots must be mostly moved sideways, that is, in the lateral direction, to avoid abutment with the open front doors. Therefore, a problem occurs because the lateral space of the painting stage is increased in accordance to lateral movement of the robots. Also, additional areas or stages must be provided in front of and behind the painting stage for opening the doors. Therefore, the size of the painting process line is increased in the longitudinal direction by these additional stages.
Additionally, when atomizers mounted on respective forward ends of the painting robots are brought close to one another, an electrostatic repulsion is generated by the high voltages applied to the individual atomizers. Thus, it is impossible to achieve a good paint job. Accordingly, in order to avoid this, it is often necessary when the front region or the rear region of the vehicle body is painted to have the atomizers of the pair of painting robots, which are located on the left side and on the right side, brought far apart from each other. One of the robots is once kept inoperative and is positioned away from the other painting robot. Therefore, the working efficiency of the robots is lowered and thus the cycle time is increased.
Additionally, with the foregoing known process for painting the inner panel region of a 2-door type motorcar vehicle body, painting of the inner panel portions of the door regions is carried out only by the rear painting robots. Therefore, the area to be painted by the pair of rear painting robots is much larger than the area to be painted by the front painting robots. Thus, the front painting robots have a lower working efficiency, while the painting working time by the rear painting robots is long which increases the cycle time.